1. Field of the Invention
The present invention relates to an information processing apparatus and method, and a storage medium and, more particularly, to an information processing apparatus connected by a serial interface such as IEEE 1394, a method therefor, and a storage medium which stores a computer program product for realizing the method.
2. Description of Related Art
When a plurality of devices are to be connected by a bus using a digital interface defined as IEEE 1394-1995 (High Performance Serial Bus) (to be referred to as a xe2x80x9c1394 serial busxe2x80x9d hereinafter), e.g., when a printer and a personal computer or a digital camera as a host device are to be connected using the 1394 serial bus, two methods, i.e., isochronous transfer and asynchronous transfer can be used to transfer data between the devices.
Isochronous transfer can advantageously synchronize data transfer timing to define the relationship between the time and amount of data to be transferred. For isochronous transfer, however, a synchronous packet (CSP: Cycle Start Packet) for synchronization must be periodically transmitted. A node which transmits this CSP is called a cycle master, so a node must have a function to serve as a cycle master (to be simply referred to as a xe2x80x9ccycle master functionxe2x80x9d hereinafter).
To the contrary, asynchronous transfer cannot establish a predetermined relationship between the time and amount of data to be transferred. However, since the cycle master is unnecessary, the cycle master function need not be incorporated, resulting in a lower device cost. The cost of a consumer device such as a digital camera may be reduced by omitting the cycle master function.
Although a bus requires at least one node having the cycle master function, only devices without any cycle master function may be connected to the bus. In such a case, data cannot be transferred because no cycle master is present. Therefore, even when, e.g., a digital camera without any cycle master function and a printer are directly connected by the IEEE 1394 serial interface, neither sides can obtain information, so printing cannot be performed.
It is an object of the present invention to provide an information processing apparatus capable of data transfer even when devices without any cycle master function are connected, or no cycle master is present on a bus, a method therefor, and a storage medium which stores the method. According to an aspect of the present invention, there is provided an information processing apparatus for controlling data transfer between devices which are connected by a serial bus, said apparatus comprising: first determination means for determining whether a cycle master necessary for isochronous transfer is present on the serial bus; second determination means for determining whether a destination device of data transfer can be performed the isochronous transfer; and setting means for setting a transfer mode of data transfer in accordance with the presence/absence of the cycle master and the possibility/impossibility of the isochronous transfer of the destination device.
According to another aspect of the present invention, there is provided an information processing apparatus for controlling data transfer between devices which are connected by a serial bus, said apparatus comprising: acquisition means for logging in a data transfer destination to acquire type information of the transfer destination; first determination means for determining whether a cycle master necessary for isochronous transfer is present on the serial bus; second determination means for determining whether a destination device of data transfer can be performed the isochronous transfer; and setting means for setting a transfer mode and a transfer parameter of data transfer in accordance with the presence/absence of the cycle master, the possibility/impossibility of the isochronous transfer of the destination device and the type information.